I'm going to tell you why you'll want to use flash (for portraits). Some of this is opinion, based on previous bad experiences. :) However, if you like working with slow shutter speed at high ISO and a wide open lens, then that's a different story. Instead, I'm speaking here of more formal portraits, like ISO 100 and f/8 and 1/200 second.
Questions about acquiring the cheapest possible continuous light kit for home portraits are very frequently seen on forums (everyone seems to start with a similar thought).
Would it improve my indoor shots, and have any value in learning and experimenting with lighting technique? Or is it such poor quality that I should just avoid it?
It's not about "quality" exactly, it is more about being continuous lights. Hot light bulbs are a real pain, our subjects may tend to sweat, but the problem is such 500 watt bulbs are still dim for photography. In the brightest part of your house, maybe a well lighted kitchen or bathroom, count the watts of all the bulbs, and then try a normal sunshine daylight exposure (EV 15, f/16 1/125 second ISO 100), and see what you get.
Continuous lights can be very good for table top or still life, possibly even preferred then, because we can see continuous light to adjust and judge the lighting, and also, the camera can meter it (and zero recycle time between shots). Then it is no problem to necessarily use a long shutter speed to accumulate sufficient light. But artificial continuous is simply insufficient light for portraits of humans. Humans move, especially kids, and we need a faster shutter speed. You will struggle with 500 watts, tying to make all your maximums work (1/30 second f/2.8 ISO 400). It never really does. It can of course be better if willing to crank ISO up a few stops even higher. But keep the lights turned OFF at every opportunity. Two of these bulbs mimic a 1000 watt room heater. The subject literally tends to sweat. More details about differences in flash and continuous (2 pages there).
A speedlight flash (like a $59 Yongnuo YN-560 II) is rated by Guide Number, maybe regular fully powered is GN 92 (feet) at ISO 100, 24 mm zoom. That means maximum power direct flash at f/9.2 at 10 feet, ISO 100 (or f/18.4 at 5 feet), at any shutter speed up to camera maximum sync speed, probably 1/200 second. It will be a couple of stops less in an umbrella, but the flash is still very usable. This is greatly more light than the continuous 1/30 second f/2.8 ISO 400, maybe four stops more light (like day and night). An umbrella is used "close as possible" anyway, to be a soft light. Plus you can turn a flash down when its too much, and it will Not heat up your room, and its speed stops motion better than shutter speed can (is called speedlight).
Studio lights have better studio features than speedlights. They are designed to mount all manner of lighting modifiers like umbrellas, softboxes, grids, snoots, etc. Good ones are fan cooled, etc. And they offer more power of course. Studio lights are rated as watt seconds of electrical energy input. We call it power, but technically, it is of course energy. A regular fully powered speedlight will compare at about 75 watt seconds. Some speedlights are a little smaller, and of course, some studio lights are much bigger (and too big can be a bigger problem than too small... we can only turn them down so much, but we can always increase ISO a little)..
Speedlights do work well in umbrellas (see Mounting Speedlights in Umbrellas). Compared to studio lights, speedlights are relatively low power (typically equivalent to 60 or probably 75 watt seconds), but umbrellas are normally used very close anyway (main light essentially as close as possible, for the soft light). The built-in speedlight reflector is no disadvantage for umbrellas ((24 mm zoom is 78x60 degrees, and I normally use 24 mm mounted at full umbrella shaft length). Do think reflected umbrellas, IMO shoot-through is a very special case only for very close distances, due to excessive spill, wasting 2/3 of the power out the back side (but the shoot-through can be placed VERY close, when it may not matter). See some speedlight power examples.
You can use Maximum Shutter Sync Speed (often 1/200 second) with flash, but up close, with the reflected umbrella fabric at about four feet from subject (and at ISO 100), stopping down more then to f/8 might be difficult for speedlights. (Qualification, you might use f/16 with the umbrella very close for macro, but portrait views usually need the light stand pole at about 2 feet, which puts the fabric at about 4 feet). Just trying to say you may prefer f/5.6 for the faster recycle speed, which can be slow at maximum power level. You will normally want manual flash mode or manual units for portrait work. Then my choice for indoor portraits is to use a PC sync cord to nearest light (normally the fill light near the camera) and optical slaves on all others (but radio triggers work too, see Triggering).
Compact fluorescent lamps: Fluorescent efficiency is higher, and we do see kit fixtures with maybe five 28 watt CFL bulbs which is 140 watts total, which is roughly the equivalent light of a 500 watt incandescent, but with only 140 actual watts. So cooler heat, but not any brighter - shutter speed still decimates the watt seconds, so you'll still need low shutter speed, high ISO, and wide aperture. Physically, these monstrosities are ludicrous in an umbrella. Just something to sell, easy to make, but hardly a smart design. In the picture at right (intended as a Bad example), how much of the light can hit the umbrella? Do realize what it shows. Some light does go into the umbrella, but most of the light goes out the side, spill flooding the room, but missing the umbrella and the subject altogether. A speedlight does work fine in an umbrella (typically 24 mm zoom mounted at full shaft length in a reflected umbrella, which should have the black cover on it). But this side loss is one reason CFL seems a deficient plan in umbrellas.
CFL makes better sense in a softbox (which is a reflector to direct all the light forward). This scattering is good inside a softbox to diffuse it. This degree of light is still marginally usable for photography. You'll still be hoping to work at ISO 400 1/60 second f/2.8 (if the light is placed close enough).
See more discussion and samples of this flash vs. continuous light difference.
Spectrum: CFL bulbs come in colors, Warm, Cool, Daylight, but their color is not as "complete" or perfectly matched as incandescent or flash. Even if the CFL lamp is called "Daylight", no fluorescent has a continuous color spectrum, which makes matching White Balance be a harder problem, an exact match is never possible. Because of this, fluorescent lamps have a CRI rating (Color Rendering Index). Their spectrum is a few discrete lines vs. a continuous spectrum. When choosing fluorescent bulbs, a high rating (CRI 80+) has better color - not perfect, but better, pretty close, often nearly acceptable. CRI is Not about color like Daylight or Warm or Cool, but is about quality of the light due to its incomplete spectrum. CRI is very important about fluorescent or LED, but unnecessary about incandescent or sunlight or flash. A lower CRI is poor for color photography (and also poor in the closet where the wife selects her clothing - to see color correctly, she wants high CRI too, CRI 80+). Perhaps high CRI is often "good enough", most colors will look OK, but the colors not in its spectrum won't look right. In contrast, incandescent lamps do have a continuous spectrum and incandescent is the definition of theoretical maximum CRI 100. Incandescent may be orange, which we adapt to, but it can easily be matched, all of the spectrum is present (tungsten filaments). Sunshine is continuous too, and flash is very close, but fluorescent and LED lights simply are not continuous spectrum.
But the biggest problem is that artificial continuous light is not very bright photographically. Unless you are Hollywood and can provide big generators and really HUGE lights. :) The only reason they do it is because movies require continuous lights.
This is why flashes are routinely used for portraits. Sure, everyone is attracted to the low price of the incandescent continuous lights at first, but due to low light levels (and heat), those buyers either give up, or they turn to flash (except maybe for the still life mentioned). Continuous lights are simply not sufficient light for any major photographic use.
Studio flash models typically range from 150 to 1200 watt seconds, some are 2400 watt seconds. 150 to 300 watt seconds is an ideal value for home portraits. There are of course bigger uses that need more power (typically for greater distances), but you will still turn 150 watt seconds down for umbrella or softbox portraits (if the lights are placed appropriately close to be a soft light). And frankly, bigger flashes can be a real problem being able to turn them down enough. The color typically shifts toward red then too.
The way to compare lights is that doubling watt seconds is one stop brighter. Same way when using them, turning them down to half power is one stop less exposure. So 150 watt seconds is one stop more power than a speedlight (one stop is a lot). The studio light also recycles faster, and has a fan to allow rapid shooting, and accepts many more lighting modifiers (softboxes, etc). In many cases, it may even cost less than a fancy branded speedlight.
The speedlight at 75 watt seconds is smaller, and is used more near full power in an umbrella, slightly marginal, but it does work. It has limits (low power, slow recycle, easily overheats, cannot mount most light modifiers), but it works. Speedlights work well in an umbrella. Fully powered speedlight portraits at ISO 100 f/8 1/200 second in close white reflected umbrellas are possible (using lower power would need more aperture, but would recycle faster between shots). A 150 watt second studio light in a softbox is probably turned down to 1/2 or 1/4 power anyway (depending on distance). A 320 watt second light is turned down even more. But a larger light will be necessary in some cases, like in bright sun or for greater distance (lighting the basketball court maybe). To overpower the sun, you will need more (depends on flash distance). But the idea of buying a large light for just in case we need it, but always having to turn it down so much for portraits, if we even can, is a very poor plan. Instead of always suffering with a too-large light, the need is for different lights for such different purposes. 150 to 300 watt seconds is plenty for living room portraits, and 75 watt second speedlights usually can do a very creditable job (they will just be working near full power level).
We can pay $1000 or $2000 for one monolight, and some users do. At a more affordable level, the $500 Einstein has much attention now. But the inexpensive ones create light too, and just to offer an idea of the concept, the way I interpret the specs on some popular inexpensive monolights is:
|Flash specs||Alienbees B400||Alienbees B800||Impact 160||Impact 300||Flashpoint 320M||Flashpoint 620M|
|Watt seconds||160 WS||320 WS||160 WS||300 WS||150 WS||300 WS|
|Max Recycle time||0.5 second||1 second||2 seconds||2 seconds||1 second||1.5 second|
|Flash duration||1/6000 second||1/3300 second||1/1000 second||1/800 second||1/1000||1/1000|
|Power steps||6 stops to 1/32||6 stops to 1/32||4 stops to 1/8||4 stops to 1/8||6 stops to 1/32||6 stops to 1/32|
|Modeling light||150 watts||150 watts||60 watts||100 watts||100 watts||150 watts|
|AC power||120 VAC||120 VAC||120 VAC||120 VAC||130 VAC or DC||130 VAC or DC|
|Price||$225||$280||$180 incl stand||$239 incl stand||$100||$190|
|Warranty||2 years or 60 day money back||1 year||Doesn't say|
|Link||Alienbees||Impact 160||Impact 300||FlashPoint 320M||FlashPoint 620M|
My own choice was Alienbees, but the point here is NOT to recommend a flash. The point is to cause awareness of certain features, or the lack of them.
This group of inexpensive USA flashes do not work on 240 volts AC. These are USA sources, with advantage of being very reputable firms which stand behind them.
A few terms for beginners:
Auto Dump - means when adjusting power lower, the flash automatically discharges the flash capacitor to reach the lower power. Otherwise you have to trigger the flash once, power won't change until it recycles next time. The Impact limited Auto Dump means the flash does it, but by actually automatically flashing when you turn power down. The Flashpoints do the same, but their specs are pretty casual, not sure I believe every word, but they don't spec it. The Alienbees are real Auto Dump, they don't flash when power is turned down, Auto Dump just bleeds the power off automatically. Speedlights don't need Auto Dump, not an issue for them. All but the cheapest studio lights do Auto Dump. This can take a few seconds to discharge, until the Ready LED.
Fan cooling - Prevents overheating, and allows more rapid flash shots. With no fan, the Impacts include substantial warnings about heat, say to allow it to cool after rapid flashing. All fans are not equal of course. Speedlights don't have fans, but all but the cheapest studio lights will have a fan.
Flash Duration (for most monolights) is fastest (shortest) at full power (t.5 value shown), and is roughly twice longer at minimum power. However, the Impact lights specify duration the opposite way (full power is slowest), implying a speedlight type of control (which unless it is an error, it of course conflicts with the need for Auto Dump?) I can't tell what the Flashpoint does, their specs are not specific enough.
Recycle time is longest at full power (value shown), and much faster at lower power. Recycle time is the "recharge" time between shots, before the next shot can work. A larger flash has a larger capacitor that takes longer to refill, but also a larger flash power supply and efficiency affects recycle time.
The cheapest imports may not have auto dump, or a fan, and probably recycle slower, or power may not turn down low enough, or a slower duration, or may have tiny modeling lights. Check availability of flash tubes, the cheapest do not have replaceable flashtubes. Don't assume unspecified features exist. The unknown Chinese brands won't offer any support for repair or parts or warranty. A reseller might provide a warranty claim.
Please know that comparing guide numbers or exposures (like f/8 at full power) can be very misleading, because output depends on the reflector too - how the reflector choice distributes the power over a large field. For example, speedlights have a different guide number at every zoom value. Efficiency is a factor too, but a wider angle reflector requires more power to illuminate the wide area than a flash with a more narrow reflector, which concentrates a narrow brighter beam. This reflector point is a big deal.
B&H (Impact) and Adorama (Flashpoint) are online retailers of the highest reputation, and these imported lights are their house brands. They do not manufacture flashes, and I suspect they don't offer any service, but they can offer warranty, at least on their house brand. Very different than Ebay sellers with no contact data. Alienbees are direct sales only from the manufacturer www.paulcbuff.com in Nashville, who has influenced flash design for decades. They are the most popular brand sold in the U.S., and their service, including after warranty, is simply legendary. See Google Alienbees or Einstein.
Another difference is that studio lights all use different systems of attaching lighting modifiers, such as softboxes or grids, etc., so we have to use what fits. Exception is that umbrellas should mount on all lights (except Elinchrom uses a special 7 mm hole for their umbrellas, so the standard 8 mm umbrella shaft diameter will not fit them). So there are differences in the selection and range and prices of modifiers available to fit each light. If anticipating that you will grow your hobby, you might check ahead that a plentiful choice of options are available. It may also be instructive to check price and availability of parts, like replacement flashtubes or other parts.
Triggering: All studio lights are manual lights. They are triggered by a PC sync cord, or also each unit includes a built-in optical slave that is triggered in sync with other manual lights. If the camera does not have a PC sync connector, you can add a hot shoe accessory that adds one, I use a Nikon AS-15, but there are cheaper ones, but you do want one with the wheel lock to keep it from sliding. I even use the AS-15 on cameras with a PC connector, it works better, more secure. Or you can add various radio triggers if desired. Either way, you only have to trigger the near light, and it will trigger the optical slaves in all the others. My portrait camera is on a tripod, and the fill light is back very near the camera (the cord is Not in the way), so my preference is the PC sync cord to the near light, and its flash triggers all the slaves anywhere. Works perfect indoors. Realize that the slaves are triggered by the full working power of the flash, not some minimal power like the Commander.
The camera cannot meter manual flash. It's not hard to tweak in exposure of one light by eye, maybe two, but a flash lightmeter will be extremely useful for multiple lights (used to set each light to a precisely known power relationship, called lighting ratio). I also use the same PC sync cord to meter each light individually. It's not just about exposure, it's easy to tweak the camera exposure by eye, but this is also about setting the lighting ratio, the known difference in the lights, to produce the specific desirable gradient tonal shading.
Lighting ratio is a very important control. We don't just set two lights out there on either side of camera. Instead, there are two important properties of Main and Fill, about intensity and location:
See a typical lighting setup.
My choice was that I have four Alienbees (two each 160 WS and 320 WS). Inexpensive (primarily because they are sold direct by manufacturer in Nashville), but these are the good inexpensive ones. Fully featured, and extremely decent performance wise. I've used them ten years, and they are still all that I need. One did finally fail recently, but a $40 repair charge fixed it fast (Their service is a legend). Four lights are used for Main, Fill, background, and hair. Since the Main light is usually placed very close (my 160 watt seconds in a Large 42" softbox at about 30 inches, and ISO 100 f/8 is nearer to 1/4 power than to 1/2 power). My Fill light umbrella is back above the camera, maybe ten feet. In that case, I would suggest one choice is starting with one 160 WS light, and one 320 WS light. Then you're ready for most indoor things, and if you get into it, you'll probably add more lights later. You can always meter them to set them equal if desired, but if you're just going to put one light on either side of camera, you'd probably prefer two identical lights. But the Main/Fill concept is much better lighting.
Continuous lights - Incandescent and CFL
Studio lights (flash)
Certainly any flash is greatly more light than continuous bulbs, allowing desirable camera settings. You've seen what your hot shoe flash can do. But using flash has differences, may require a bit of getting used to.
Flash spooks some, but it's easy if you let it be easy. Flash is an added light that we control. If result is too bright, turn it down. If not bright enough, turn it up. When you realize this is YOUR job now, it becomes easy. If using manual flashes, a light meter helps a lot (especially true for multiple lights), to actually know what we're doing. If TTL, flash compensation is how we control what the camera is doing. If not at the right angle, move it so it is. Make it be like you want it. This does not happen automatically, so the first thing to realize is that it is YOU that has to control this. If you're willing to get involved, then flash is not hard.
We can't see the flashes lighting effect except in a test picture (rear LCD of camera). Bigger studio lights have 250 watt incandescent modeling lights in them, which help to see shadows and catchlights, but the illumination levels probably won't show accurate ratio, so a test picture is the final word. Incidentally, these modeling lights can be left on during the picture, without even affecting the flash picture.. because they are too dim for say f/8 1/200 ISO 100, a very black picture without the flash. The flash overwhelms them. This is something you should verify once, pull the camera sync cord and take the same picture without flash, just modeling lights on. Then at your sessions regular exposure, you want to see a black picture, because incandescent lights are orange.
The camera cannot meter flash (TTL systems excepted). You can use a handheld incident meter, which are fabulous, and precise, or you can trial and error tweak it in (for one or maybe two lights, but more lights need a meter, to have a clue about ratio, and to easily reproduce the same setup next time). Tweaking the camera exposure without a meter is easy, but the advantage of the meter is in setting the power of multiple lights to their exact known relationships... lighting ratio. A common plan is the Main light is quite close, high, and towards the side (maybe near 45 degrees wide, and up to 45 degrees high, from subject). A Fill light is more frontal, near the lens axis, which has to be back by the camera so the lens can see around its umbrella. For color images, the Fill is often set about one stop less bright at the subject than the main light (ratio). For TTL with the Commander, just set the fill group to -1 EV compensation. Equal lights are flat, normally a bad thing for portraits.
There are many choices, and also other ways, but my notion is a speedlight in a softbox just doesn't fit. Light does come out, but studio lights are used bare bulb in softboxes (180 degree wide light), which does not describe speedlights. Speedlights do work very well in an umbrella. Just for an idea, my notion of a good low price starter kit for two speedlights is:
Smith Victor UK2 45 inch Umbrella Kit $120. These will be excellent for umbrellas on either speedlights or the monolights above. However, large softboxes will need stronger stands, with wider footprint.
Quantity One: Optional. Radio trigger Yongnuo RF-603NII-N3 Wireless Flash Trigger Kit for Nikon D90 / D7000 / D7100 / D5000 / D5100 / D5200 / D3100 / D3200 / D600 $30 for package of two transceivers (needs 4 AAA alkaline batteries). Get the version for your camera model, -N1 for 10-pin D300, D700, D800, D4, etc. The cable is only for the remote shutter function, not used for flash. A transceiver can be either the transmitter on camera hot shoe, or it can be the receiver on the flash. Only one package of two transceivers is needed, because the second flash can use its slave mode (triggered in sync from the flash of the radio flash). If you did want another radio trigger for it, you only need one more transceiver, total of three... one on camera hot shoe and one on each flash. But the flashes slave will easily do the job.
FWIW, radio triggers are an optional expense. I only mention them because people imagine they need them, but I don't use a radio trigger indoors, they are just something else that needs to be messed with (more connections, settings, batteries, power switches, etc). Studio lights already have good optical slaves, so I just use the PC sync cord that comes with the studio flash, to the fill light which is right at the camera. Then it easily triggers the optical slaves on all the other lights. The same PC sync cord is also used with the light meter to meter the individual lights. You can add a PC connector to a camera without one with an adapter, like the Nikon AS-15.
Quantity Two: Yongnuo YN-565EX flash $81 each (will do remote TTL from the Commander, or will do Manual flash too). Commander is standalone, does not use any radio trigger. Set the fill light about -1 EV for lighting ratio. It is quick setup, but two lights will likely be the maximum this way. For learning any serious portrait effort, I'd suggest regular manual flash mode (for the greater control if you have a flash meter).
This setup will work, all you need. Except, you may need to provide a background behind the subject (a few feet back), which can be many things... whatever you want to see there. Maybe a purchased muslin or seamless paper background, but it can be a wall, a fireplace, a white sheet or foam board, etc. White things farther from the light will look gray unless you provide another background light for it. Another option is to provide a hair light, from high behind, to highlight the hair, and/or to separate dark hair from a dark background. This is a sparkle in the hair, like catchlights are sparkles in the eyes. A sheet of letter size paper, wrapped long ways around the speedlight head with a piece of tape, can make a snoot tube to project a narrow beam of light (keeping it off of shoulders, etc.) More than two lights is a problem for the camera Commander, but a manual flash system can just use the extra flashes slave, easiest thing.
See details about mounting speedlights in umbrellas. Umbrella shaft length is proportional to umbrella size, and my notion to fill the umbrella is 24 mm zoom on the speedlight, with it mounted back near full shaft length.
See a typical lighting setup.
I'm hoping this is useful information to newbies wanting to do portraits.